This invention relates to improved nozzle means for rotary drill bits, and more particularly to improved nozzle means for directing drilling fluid first against the side wall of the formation being cut and then underneath the roller cutters of drill bits.
Heretofore, such as shown in U.S. Pat. No. 4,741,406, various types of discharge nozzles for discharging drilling fluid against roller cutters of a rotary drill bit have been utilized. Some of the prior nozzles have been positioned to discharge drilling fluid in a direction toward the surface or side of the roller cutters and some of the nozzles have been positioned and constructed to discharge drilling fluid in a direction against the side wall of the bore hole. However, the arrangement of such discharge nozzles heretofore has not provided an optimum use of hydraulic cleaning action for the efficient cleaning of the hole bottom including the corner of the hole, while adequately cleaning the cutting elements.
The most important area of the hole to adequately clean is the corner of the hole at the juncture of the side wall with the bottom where cuttings are most likely to pack particularly in so called sticky formations. Also the corner is stronger than the flat hole bottom and is more difficult to drill. It is also important to effectively clean the rest of the hole bottom. To most effectively clean the formation it is important to achieve a high tangential velocity sweeping across the surface of the formation, both at the corner of the hole and the bottom of the hole. Also in sticky formations the cutting elements need to be cleaned to more efficiently penetrate the formation. It has been found that it is most desirable to clean the formation and the cutting elements during engagement and just prior to engagement with formation.
Prior art drill bits have not effectively cleaned the corner of the hole and then effectively cleaned the hole bottom because they lack a high velocity flat stream sweeping across the corner of the hole and the hole bottom in a direction tangential to the hole bottom beneath the cutting elements of an adjacent roller cutter.